Acryloyl-functionalized linear polydimethylsiloxanes can have a satisfactory oxygen permeability yet suffer from hydrophobicity, thereby repelling water and increasing the incidence of corneal staining. That is, introduction of a siloxanyl group for the purpose of increasing oxygen permeability can negatively impact other properties of the composition. Further, when an acryloyl-functionalized polydimethylsiloxane is copolymerized with a hydrophilic monomer (e.g., 2-hydroxyethyl(meth)acrylate) in order to increase the hydrophilicity, phase separation can occur due to the static repulsion between the polar hydroxyl group and the nonpolar siloxanyl group, so that a transparent polymer cannot be obtained. Accordingly, such compositions can have poor optical quality.
Moreover, some acryloyl-functionalized polydimethylsiloxane compositions produced by an addition reaction between an epoxy compound having a siloxanyl group and (meth)acrylic acid can contain unsatisfactory concentrations of undesirable impurities, for example, epoxide or diol moieties that can have irritating properties when the compositions are used as, for example, contact lenses and intraocular lenses.
Therefore, there remains a need for methods and compositions that overcome these deficiencies and that effectively attain a satisfactory balance between improved oxygen permeability and hydrophilicity while achieving an acceptably low concentration of undesirable impurities.